Structure Elucidation and Anticancer Activity of 7-Oxostaurosporine Derivatives from the Brazilian Endemic Tunicate Eudistoma vannamei

The present study reports the identification of two new staurosporine derivatives, 2-hydroxy-7-oxostaurosporine (1) and 3-hydroxy-7-oxostaurosporine (2), obtained from mid-polar fractions of an aqueous methanol extract of the tunicate Eudistoma vannamei, endemic to the northeast coast of Brazil. The mixture of 1 and 2 displayed IC50 values in the nM range and was up to 14 times more cytotoxic than staurosporine across a panel of tumor cell lines, as evaluated using the MTT assay.

The Use of Ultrasonography to Study Teratogenicity in Ruminants: Evaluation of Ipomoea carnea in Goats

Background: Ipomoea carnea (I. carnea) is a poisonous plant found in Brazil and other tropical countries that often poison livestock. The plant contains the alkaloids calystegines and mainly swainsonine, which inhibit cellular enzymes and cause systematic cell death. The objective of this study was to evaluate the perinatal effects of I. carnea in goats. Methods: Forty-seven pregnant goats were randomly allocated into 5 treatment groups and given the following doses (g/kg BW) of I. carnea: 0 (IC0), 1.0 (IC1), 3.0 (IC3), 5.0 (IC5) and 7.5 (IC7). The treatment animals were given fresh I. carnea from day 27 of gestation to parturition. Weight gains and serum biochemistry were evaluated. Fetuses were evaluated using ultrasonographic measurements. Results: Goats from the IC7 group showed clinical signs of poisoning. Ultrasound examination revealed that I. carnea feeding in all treatment groups reduced fetal movement compared to the controls. There was an increase in the total number of birth defects (retrognathia and arthrogyposis) in the IC7 and IC5 groups compared to the controls. Conclusion: The results show that I. carnea has teratogenic potential in goats. In addition, ultrasounds were useful in evaluating fetotoxicity and teratogenicity. Birth Defects Res (Part B) 00:17, 2012. (c) 2012 Wiley Periodicals, Inc.

Total Synthesis of (+)-trans-Trikentrin A

Several syntheses have already been reported for cis-trikentrins and herbindoles, which are indole alkaloids unsubstituted at the C2 and C3 positions that bear a trans-1,3-dimethylcyclopentyl unit. Herein, we describe the first asymmetric and stereoselective synthesis of the more challenging trans-trikentrin A as its naturally occurring isomer. Different approaches were investigated and the strategy of choice was a combination of an enzymatic kinetic resolution and a thallium(III)-mediated ring contraction. The antiproliferative activities of the natural product and related intermediates have been tested against human tumor cell lines, leading to the discovery of new compounds with potent antitumor activity.

Biosynthesis of Two Dihydropyrrole-Polyketides from a Marine-Derived Penicillium citrinum

Feeding experiments with C-13-labeled precursors were performed in order to establish the biosynthesis of two N-acylated dihydropyrroles, (8E)-1-(2,3-dihydro-1H-pyrrol-1-yl)-2- methyldec-8-ene-1,3-dione (1) and 1-(2,3-dihydro-1H-pyrrol-1-yl)-2- methyldecane-1,3-dione (2), isolated from the cultures of a marine-derived Penicillium citrinum. The biosynthesis of both, 1 and 2, involves the incorporation of acetate, methionine and ornithine.

Aplicação de espectrometria de massas com ionização por elétron na análise de alcaloides do mulungu

Erythrina verna is a medicinal plant used to calm agitation popularly known as mulungu. We purchased the barks of E. verna from a commercial producer and analyzed the alkaloid fraction of the bark by CG-MS and HRESI-MS. Five erythrinian alkaloids were identified: erysotrine, erythratidine, erythratidinone, epimer, and 11-hydroxieritratidinone. Here we report the compound 11-hydroxieritratidinone for the first time as a natural product.

Exogenous influences on plant secondary metabolite levels

Plant secondary metabolites are a group of naturally occurring compound classes biosynthesized by differing biochemical pathways whose plant content and regulation is strongly susceptible to environmental influences and to potential herbal predators. Such abiotic and biotic factors might be specifically induced by means of various mechanisms, which create variation in the accumulation or biogenesis of secondary metabolites. Hence the dynamic aspect of bioactive compound synthesis and accumulation enables plants to communicate and react in order to overcome imminent threats. This contribution aims to review the most important mechanisms of various abiotic and biotic interactions, such as pathogenic microorganisms and herbivory, by which plants respond to exogenous influences, and will also report on time-scale variable influences on secondary metabolite profiles. Transmission of signals in plants commonly occurs by 'semiochemicals', which are comprised of terpenes, phenylpropanoids, benzenoids and other volatile compounds. Due to the important functions of volatile terpenes in communication processes of living organisms, as well as its emission susceptibility relative to exogenous influences, we also present different scenarios of concentration and emission variations. Toxic effects of plants vary depending on the level and type of secondary metabolites. In farming and cattle raising scenarios, the toxicity of plant secondary metabolites and respective concentration shifts may have severe consequences on livestock production and health, culminating in adverse effects on crop yields and/or their human consumers, or have an adverse economic impact. From a wider perspective, herbal medicines, agrochemicals or other natural products are also associated with variability in plant metabolite levels, which can impact the safety and reliable efficacy of these products. We also present typical examples of toxic plants which influence livestock production using Brazilian examples of toxicity of sapogenins and alkaloids on livestock to highlight the problem. (c) 2012 Elsevier B.V. All rights reserved.

Systematic UPLC-ESI-MS/MS Study on the Occurrence of Staurosporine and Derivatives in Associated Marine Microorganisms from Eudistoma vannamei

Former bioactivity-guided analysis of the marine invertebrate Eudistoma vannamei led to the isolation of staurosporine derivatives, which revealed strong cytotoxic activity against several human cancer cell lines. The occurrence of such alkaloids in E. vannamei may be correlated to the presence of associated biota, such as Streptomyces bacteria. In agreement to this hypothesis, marine microorganisms associated with E. vannamei were recovered and cultured, leading to a total of 84 isolated bacterial strains. Gas phase fragmentation reactions of staurosporine and derivatives were systematically studied and the analyzed results further supported by computational chemistry studies. The resulting fragment patterns were used to search for the presence of different derivatives in extracts of isolated microorganisms, thereby using LC-MS/MS analysis in MRM mode. These results evidenced that one isolated Streptomyces sp. was able to generate staurosporine, while none of the hydroxy-7-oxo derivatives were detected. Finally, significant cytotoxic activity against human cancer lines was observed for one of the extracts.

History and Epistemology of Science in the Classroom: The Synthesis of Quinine as a Proposal

The history of the quinine synthesis can be used as a case study to emphasize that science is influenced by social and historical processes. The first efforts toward the synthesis of this substance, which until recently was the only treatment for malaria, were by Perkin in 1856 when, trying to obtain quinine,,. he synthesized mauveine. Since then, the quest for the total synthesis of quinine involved several characters in a web of controversies. A major step in this process was made in 1918 by Rabe and Kindler, who proposed the synthesis of quinine from quinotoxine. Twenty-six years later, after obtaining the total synthesis of quinotoxine, Woodward and Doering announced the total synthesis of quinine. However, the lack of experimental details about Rabe and Kindler's process, associated with Woodward and Doering's failure to reproduce it, raised a series of doubts about the synthesis. Stork and colleagues questioned the veracity of the experimental data and even the scientific reputation of the involved researchers. Doubts remained alive until 2008, when Williams and Smith reported, not without reservations, the reproducibility of Rabe and Kindler's protocol. The scientific knowledge as a social and historical development, its legitimating process, and the absence of neutrality in science constitute aspects that can be discussed from this case study, providing significant contributions to science education, in particular, to the initial or continued training of chemistry teachers.

Utilização de detecção por espalhamento de luz evaporativo para a análise de produtos naturais

The interest in the use of evaporative light scattering detector (ELSD) for the analysis of different classes of natural products has grown over the years. This is because this detector has become an excellent alternative compared to other types of detectors, such as the refractive index detector and the ultraviolet (UV) detector. This review describes the basic principles of ELSD functioning and discusses the advantages and disadvantages in using an ELSD for the analysis of organic compounds. Additionaly, an overview, covering the last 23 years, of ELSD applications in natural products analysis (saponins, terpenes, carbohydrates, glycosides, alkaloids, steroids, flavonoids, peptides, polyketides, coumarins and iridoids) is presented and discussed.

Fitoquímica e quimiossistemática de Conchocarpus marginatus e C. inopinatus (Rutaceae)

Phytochemical studies of the leaves and stem have led to the identification of the known acridone alkaloids arborinine, methyl-arborinine, 1-hydroxy-3-methoxy-N-methyl acridone, xanthoxoline, 1,2,3,5-tetramethoxy-N-methylacridone, toddaliopsin C and the new seco acridone alkaloid inopinatin. The known quinoline alkaloids 2-phenyl-1-methyl-quinolin-4(1H)-one, 2-phenyl-1-methyl-7-methoxy-quinolin-4(1H)-one, dictamnine, and the coumarins scopoletin and marmesin were also isolated. The isolated compounds and the distribution of secondary metabolites, which are systematically important, obtained from literature, clearly confirmed that some species formerly described in the genera Angostura and Galipea in fact shall belong to the genus Conchocarpus.

Aplicação de espectrometria de massas com ionização por elétron na análise de alcaloides do mulungu

Erythrina verna is a medicinal plant used to calm agitation popularly known as mulungu. We purchased the barks of E. verna from a commercial producer and analyzed the alkaloid fraction of the bark by CG-MS and HRESI-MS. Five erythrinian alkaloids were identified: erysotrine, erythratidine, erythratidinone, epimer, and 11-hydroxieritratidinone. Here we report the compound 11-hydroxieritratidinone for the first time as a natural product.

Systematic UPLC-ESI-MS/MS study on the occurrence of staurosporine and derivatives in associated marine microorganisms from Eudistoma vannamei

Former bioactivity-guided analysis of the marine invertebrate Eudistoma vannamei led to the isolation of staurosporine derivatives, which revealed strong cytotoxic activity against several human cancer cell lines. The occurrence of such alkaloids in E. vannamei may be correlated to the presence of associated biota, such as Streptomyces bacteria. In agreement to this hypothesis, marine microorganisms associated with E. vannamei were recovered and cultured, leading to a total of 84 isolated bacterial strains. Gas phase fragmentation reactions of staurosporine and derivatives were systematically studied and the analyzed results further supported by computational chemistry studies. The resulting fragment patterns were used to search for the presence of different derivatives in extracts of isolated microorganisms, thereby using LC-MS/MS analysis in MRM mode. These results evidenced that one isolated Streptomyces sp. was able to generate staurosporine, while none of the hydroxy-7-oxo derivatives were detected. Finally, significant cytotoxic activity against human cancer lines was observed for one of the extracts.

Organocatalytic asymmetric mannich-type reactions: an easy approach to optically active amine derivatives

The topics I came across during the period I spent as a Ph.D. student are mainly two. The first concerns new organocatalytic protocols for Mannich-type reactions mediated by Cinchona alkaloids derivatives (Scheme I, left); the second topic, instead, regards the study of a new approach towards the enantioselective total synthesis of Aspirochlorine, a potent gliotoxin that recent studies indicate as a highly selective and active agent against fungi (Scheme I, right). At the beginning of 2005 I had the chance to join the group of Prof. Alfredo Ricci at the Department of Organic Chemistry of the University of Bologna, starting my PhD studies. During the first period I started to study a new homogeneous organocatalytic aza-Henry reaction by means of Cinchona alkaloid derivatives as chiral base catalysts with good results. Soon after we introduced a new protocol which allowed the in situ synthesis of N-carbamoyl imines, scarcely stable, moisture sensitive compounds. For this purpose we used α-amido sulfones, bench stable white crystalline solids, as imine precursors (Scheme II). In particular we were able to obtain the aza-Henry adducts, by using chiral phase transfer catalysis, with a broad range of substituents as R-group and excellent results, unprecedented for Mannich-type transformations (Scheme II). With the optimised protocol in hand we have extended the methodology to the other Mannich-type reactions. We applied the new method to the Mannich, Strecker and Pudovik (hydrophosphonylation of imines) reactions with very good results in terms of enantioselections and yields, broadening the usefulness of this novel protocol. The Mannich reaction was certainly the most extensively studied work in this thesis (Scheme III). Initially we developed the reaction with α-amido sulfones as imine precursors and non-commercially available malonates with excellent results in terms of yields and enantioselections.3 In this particular case we recorded 1 mol% of catalyst loading, very low for organocatalytic processes. Then we thought to develop a new Mannich reaction by using simpler malonates, such as dimethyl malonate.4 With new optimised condition the reaction provided slightly lower enantioselections than the previous protocol, but the Mannich adducts were very versatile for the obtainment of β3-amino acids. Furthermore we performed the first addition of cyclic β-ketoester to α-amido sulfones obtaining the corresponding products in good yield with high level of diastereomeric and enantiomeric excess (Scheme III). Further studies were done about the Strecker reaction mediated by Cinchona alkaloid phase-transfer quaternary ammonium salt derivatives, using acetone cyanohydrin, a relatively harmless cyanide source (Scheme IV). The reaction proceeded very well providing the corresponding α-amino nitriles in good yields and enantiomeric excesses. Finally, we developed two new complementary methodologies for the hydrophosphonylation of imines (Scheme V). As a result of the low stability of the products derived from aromatic imines, we performed the reactions in mild homogeneous basic condition by using quinine as a chiral base catalyst giving the α-aryl-α-amido phosphonic acid esters as products (Scheme V, top).6 On the other hand, we performed the addition of dialkyl phosphite to aliphatic imines by using chiral Cinchona alkaloid phase transfer quaternary ammonium salt derivatives using our methodology based on α-amido sulfones (Scheme V, bottom). The results were good for both procedures covering a broad range of α-amino phosphonic acid ester. During the second year Ph.D. studies, I spent six months in the group of Prof. Steven V. Ley, at the Department of Chemistry of the University of Cambridge, in United Kingdom. During this fruitful period I have been involved in a project concerning the enantioselective synthesis of Aspirochlorine. We provided a new route for the synthesis of a key intermediate, reducing the number of steps and increasing the overall yield. Then we introduced a new enantioselective spirocyclisation for the synthesis of a chiral building block for the completion of the synthesis (Scheme VI).

Stereoselective Catalytic Processes for the Synthesis of Polycyclic Aromatic Compounds

In this PhD-thesis, two methodologies for enantioselective intramolecular ring closing reaction on indole cores are presented. The first methodology represents a highly stereoselective alkylation of the indole N1-nitrogen, leading to 3,4-dihydro-pyrazinoindol-1-ones – a structural class which is known for its activity on the CNS and therefore of high pharmacological interest concerning related diseases. In this approach, N-benzyl cinchona-alkaloids were used for the efficient catalysis of intramolecular aza-Michael reactions. Furthermore, computational studies in collaboration with the research group Prof. Andrea Bottoni (Department of Chemistry “G. Ciamician”, Bologna) were accomplished in order to get insight into the key interactions between catalyst and substrate, leading to enantiomeric excesses up to 91%. The results of the calculations on a model system are in accordance with the experimental results and demonstrate the high sensibility of the system towards structural modifications. The second project deals with a metal catalyzed, intramolecular Friedel-Crafts (FC)-reaction on indolyl substrates, carrying a side chain which on its behalf is furnished with an allylic alcohol unit. Allylic alcohols are part of the structural class of “π-activated alcohols” – alcohols, which are more easily activated due to the proximity to a π-unit (allyl-, propargyl-, benzyl-). The enantioselective intramolecular cyclization event is catalyzed efficiently by employment of a chiral Au(I)-catalyst, leading to 1-vinyl- or 4-vinyl-tetrahydrocarbazoles (THCs) under the formation of water as byproduct. This striking and novel process concerning the direct activation of alcohols in catalytic FC-reactions was subsequently extended to similar precursors, leading to functionalized tetrahydro-β-carbolines. These two methodologies represent highly efficient approaches towards the synthesis of scaffolds, which are of enormous pharmaceutical interest and amplify the spectra of enantioselective catalytic functionalisations of indoles.

Reinigung der Vinorin-Synthase aus Zellkulturen von Rauvolfia serpentina

Abstrakt - DeutschThema: Reinigung der Vinorin-Synthase aus Zellkulturen von Rauvolfia serpentina Die Arbeit befaßte sich mit der Reinigung und Charakterisierung des Enzyms Vinorin-Synthase aus Zellkulturen von Rauvolfia serpentina. Dieses Acetyl-Coenzym-A-abhängige Enzym katalysiert im Biosyntheseweg des Alkaloids Ajmalin die Umwandlung von 16-epi-Vellosimin zu Vinorin. Mit Hilfe eines neu entwickelten Enzymaktivitätstests ist eine einfache und schnelle qualitative sowie quantitative Bestimmung der Aktivität der Vinorin-Synthase möglich. Das Molekulargewicht der Vinorin-Synthase wurde durch Größenausschlußchromatographie an Superdex 75 zu 43 kD ermittelt. Das entwickelte Reinigungsschema mit den vier säulenchromatographischen Reinigungsschritten Anionenaustauschchromatographie an SOURCE 30Q, Chromatographie an Hydroxyapatit, Anionenaustauschchromatographie an Mono Q und Chromatofokussierung an Mono P führte zu einer 340fachen Anreicherung der Vinorin-Synthase. Das nach der Reinigung durchgeführten gelelektrophoretischen Untersuchungen ermöglichten keine Zuordnung einer Bande zur Bande der Vinorin-Synthase. Mögliche Ursachen für die Nichtzuordnung einer Bande im SDS-Gel zur Vinorin-Synthase sind in einer möglichen Überlagerung eines Fremdprotein mit der Vinorin-Synthase, eine niedrige Expression der Vinorin-Synthase, die eine deutlich bessere Anreicherung erfordern würde oder der Aufbau des Proteins aus Untereinheiten, in die es während der Behandlung mit SDS zerfällt, gegeben.